.223 Rem / 6mm CM / 6,5mm CM / .308 Win / 6,5 PRC - En
At the beginning of the new shooting season many shooters especially beginners are choosing a caliber for their new rifle for precision shooting and Long Range. So let's take a look at what to expect. It is actually a sequel and the latest summary of previous articles on caliber selection, the first part on reloading and the second part on reloading...
We often encounter certain myths and "common beliefs" which unfortunately are very often simply outdated and just wrong... For example the statement about the prices of ammunition... So let's look at a comparison of the prices of ammunition in two versions. First is the economic Match ammo from the manufacturer Sellier & Bellot (they do not offer 6 CM and 6.5 PRC yet). And the second variant is Match ammo from the company Hornady specifically for each caliber in the most common weight of the ELD-M bullet which is a modern design and very successful. These bullets are also used by many shooters when reloading. Prices are according to BEAREKA's offer.
Caliber S&B price Hornady ELD-M price
.223 Remington 0,95 € 1,05 €
6mm Creedmoor ----- 2,10 €
6,5mm Creedmoor 1,10 € 1,95 €
.308 Winchester 1,20 € 2,25 €
6,5 PRC ----- 2,65 €
From these data it is clear that the calibers are arranged in ascending order not only according to the diameter of the bullet and its weight but also according to the price. The 6mm Creedmoor cartridge does not fit into the price yet - because it is not yet as common as the others. The 6.5 PRC has a bullet diameter and weight less than .308 Winchester but it's a semi-magnum round (a bit of a strange designation I know. However it is no longer a standard caliber and it does not have the performance of classic magnum calibers...). And it is not very common too. It is interesting that the Finnish Lapua which produces cartridges for reloading in the highest quality already offers for the season 2021 cartridges of all the above calibers. And that means only one thing - they also see commercial potential in these calibers...
Another common aspect is the power - the energy of the projectile. Here is a comparison of the energy of bullets at different distances and also their speed. I chose distances for all charts:
100 meters - the most common distance for zeroing and even accuracy testing
300 meters - the usual distance of shooting ranges in Europe and in our country too
500 meters - frequent distance for the Long Range and the limit of some shooting ranges
700 meters - also a frequent distance for the Long Range
1000 meters - standard distance for Long Range
To get an idea of what distances can be reached with each caliber here is another chart. There is a "transonic range" (in this case 410 m/s) beyond which the bullet is already becoming unstable. And also the distance when the speed falls below the speed of sound - the "subsonic range" (in this case 340 m/s). Accuracy at these speeds decreases significantly with standard bullets... Therefore it is considered an effective distance with conventional bullets when they still have at least 415 m/s.
Another interesting factor is the drop of the bullet (that is if we have fired at 100 meters by how much would be hit at other distances - and therefore how much we actually have to compensate. Either by using the scope turrets - clicking - or by hold over). There are two values - the first is the drop of the bullet in centimeter and the second number is how big is a difference if I was mistaken in measuring or estimating a distance of just 10 meters. And that's a very interesting piece of information - because it tells us more about "caliber sensitivity to precise distance measurements." In other words how much the caliber can "forgive mistakes". It is necessary to realize that when you come to the shooting range and they tell you: "this is 300 meters" it may not be true... It can easily be only 290..... .....and your hits will be a few centimeters higher.
The wind sensitivity is really a super important factor especially when it comes to the Long Range (over 300 meters). Because it is extremely difficult to estimate the wind correctly and only a few people can really do it. The wind is not constant especially in our conditions. Not only does it change direction and speed but it usually doesn't blow the same way all the way to the target. How each caliber can "resist the effects of the wind" is really one of the basic factors. The speed of the bullet and its ballistic coefficient play a role here. The chart shows in centimeters the deflection of the projectile at a constant air flow throughout the flight. And at a wind speed of 4 m/s, which can be easily estimated - the wind begins to bend small branches. It is also a long-term average wind speed in our area... The second number is if we misjudge the wind and it is not 4 m/s but only 3 m/s (for example it is not perpendicular but from an angle, or is slightly weaker. To properly estimate the wind is really difficult) - so the difference from the original value...
I simulated the conditions for all calibers in the same way:
Weapon weight 7.5 kg. This is a normal medium weight.
Pressure 975 hPa, temperature 15° C and humidity 50%. So normal conditions at our shooting ranges ...
The data for individual calibers are according to the manufacturer's specifications (including muzzle velocities which are for 24" barrels). These are for Hornady Match rounds with an ELD-M bullet.
The values are calculated in the ballistic program Strelok.
Caliber bullet weight G1 G7
.223 Remington 73 grs .398 .200
6mm Creedmoor 108 grs .536 .270
6,5mm Creedmoor 140 grs .646 .326
.308 Winchester 168 grs .523 .263
6,5 PRC 147 grs .697 .351
Of course, better results can be achieved if we reload ourselves. We can make a charge that can take full advantage of the weapon's potential and it is usually possible to obtain a slightly higher speed than with factory ammunition.
As I mentioned in another article it would be ideal to fire a bullet as fast as possible with the highest possible ballistic coefficient and with the least possible recoil... Which are quite conflicting requirements.
It may seem that the differences between the individual calibers are not so great in centimeters. But it depends on the point of view...
This last chart shows us the deviations if we have wrong distance by only 10 meters and we are wrong in the wind estimation by only 1 m/s (see charts above). And when I turn it into real situations:
A common target for shooting at 300 meters is an international pistol target 50/20. The center has a diameter of 5 cm. If I made a small mistake in estimating the wind (4 m/s instead of the actual 3 m/s) and the target was not 300m but only 290m then the deviations would be according to the chart. On the side the 6.5 CM is one centimeter better than the .308 Win (and that's a fifth of the size of the target). And with increasing distance it's an even bigger difference. Sometimes we shoot an A4 size target (about 30 cm high and 20 cm wide) at a distance of about 700 meters. Accuracy around 1 MOA (ie 20cm) is really difficult to maintain but the best can do it in the given conditions. And here the deviations already play a bigger role. The difference between 6.5 CM and .308 Win is almost a third of the size of the target with such a small error in estimating the wind...
In any case this comparison can (I hope) clarify a little what can be expected from which caliber. However the last criterion is missing - and that is the barrel life while maintaining the same accuracy and speed. Of course this is only an estimate but good enough for comparison...
Caliber estimated barrel life
.223 Remington 4.000
6mm Creedmoor 1.700
6,5mm Creedmoor 2.000
.308 Winchester 5.000
6,5 PRC 1.400
I have mentioned many times that for several years now I have preferred the 6.5mm Creedmoor caliber as a universal standard instead of the previously sufficient .308 Winchester. This really has the only one advantage - and that is the longer barrel life. But as I have also mentioned many times too - I would rather have great results and enjoy shooting for two years (and then change the barrel) than fight with the results for five years...
And we must not forget the fact that recoil also plays a significant role in comparing calibers. With a smaller recoil it is easier not to make mistakes and it improves the shooter's ability to use the potential of the weapon and ammunition. Thanks to the lower recoil you can also shoot faster. As an example I will mention the finals of the Kahles Dynamic Long Range Challenge 2019 in Austria. It was fired at a distance of 300 meters to 1,200 meters in a combination of dynamic and precise shooting. Due to the distances there were quite a few shooters with magnum calibers who relied on better ballistics and less "sensitivity to wind". But the shooting was really dynamic and fast and so the disadvantage of a higher recoil was manifested. Out of 64 participants 26 shooters chose magnum calibers. In the top ten it turned out as follows:
1st place - 6.5mm Creedmoor
2nd place - 6.5mm Creedmoor
3rd place - 6.5x47 Lapua
4th place - .300 Winchester Magnum
5th place - .338 Lapua Magnum
6th place - .280 Remington (7mm bullet, semi-magnum in performance)
7th place - 6mm Creedmoor
8th place - .260 Remington (6.5mm bullet)
9th place - 6.5 PRC (semi-magnum)
10th place - .300 Winchester Magnum